This is a recording of the mind train defusion exercise. It is the version that I use with mental health clients with personality disorder diagnoses, and I've modified it in the following ways:
1. It involves a fair amount of description of the physical aspects of the bridge over the track (particularly the solid brickwork), to help people who are particularly prone to fusion and dissociation to at least start the practice with a sense of being on the bridge, and to have something solid to return to during the practice.
2. Most of my clients have histories of suicide attempts, so the description of the bridge includes a high wall that they can just rest their chin on, to reduce the chances of them immediately having images of throwing themselves off. Without this kind of modification, this client group can get so dysregulated by the format of defusion exercises like this, that they don't actually manage to get on with the practice. Of course, it's not possible to stop such images showing up, and nor would you want to necessarily, as it would be helpful for people to cultivate a more defused relationship with these images. However, it's also not helpful for people to become overwhelmed emotionally before they have even started the practice!
3. The exercise has been simplified - it involves practicing defusion just with thoughts/images/memories, unlike some versions of the exercise where people are invited to picture three different trains - for thoughts, emotions and sensations. My experience is that most people find that too complicated.
4. This version of the exercise included descriptions that are likely to be meaningful to people living in the UK.
My experience is that generally clients with complex, mixed Axis I and Axis II presentations find it possible to engage with this practice and find it helpful.